Nickel coating composition and method of coating



Oct. 18, 1960 A. M. CARLSON EI'AL ,9

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United States lice NICKEL COATING COMPOSITION AND METHOD or COATING eArthur M. Carlson, Chicago, and Carl E. Prymula, Zion,

Ill., assignors to Alpha Metal Laboratories, Inc., Chicago, Ill., acorporation of Illinois Filed July 25, 1958,'Ser. No. 750,870

4 Claims. (Cl. 117-47) I The invention relates to coating surfaces withnickel and more particularly relates to a process of spray metallizingconductors and non-conductors with chemically reduced nickel.

An object of this invention is to provide a simple and inexpensiveprocess of providing a smooth, uniform coating of nickel.

These and other objects and advantages are accomplished by spraying anaqueous solution of nickel sulphate (preferably the hydrated nickelsulphate, NiSO -6H O) containing citric acid in a molar ratio of nickelsulphate to citric acid of between approximately 1.3 to 2.0 inconjunction with a reducer solution in such a manner that the solutionsconverge on the article to be coated.

in place of nickel sulphate, there can be used nickel chloride or nickelformate, in a molar ratio of such salts to citric acid of 1.3 to 2.85.

The reducer solution which we have found to give the most satisfactoryresults with the above mentioned nickel solutions is as follows:

Grams per liter of aqueous solution Sodium hydroxide 2 to 10 Sodiumhydrosulphite 20 to 80 Sodium hypophosphite 5 to 30 Table I Ratio:Thickness, mils. 3.18 0.008 2.00 0.040 1.77 0.042 1.60 0.048 1.32 0.0331.06 0.00 0.80 0.00

We obtained satisfactory results with concentrations of nickel sulphate(NiSo -6H O) of from 15 to 20 grams per liter and citric acid of between8 to 12 grams per liter, the molar ratios of nickel sulphate (NiSO -6HO) to citric acid being as stated above, i.e., 1.3 to 2.0.

The above compositions can, of course, be sold in much more concentratedsolutions, or even in a dry state and then diluted with water to makethem suitable for the process of this invention.

The temperature of the solutions during processing can be varied widely.However, the temperature limit of the reducer solution is about 140 F.,as above this temperature it starts to decompose. Suitable temperaturesareap proximately 70 F. to

tions, and 70 F. to 180 F.-for the metal solutions.

For cold spraying of plastics, that is, tempcratures of 60 F.i to F.,'weobtain preferred results bysensitizing the plastic surface with 2 to 10grams of SnCl: per

liter-of aqueous solution, preferably containing .5- to 2 grams perliter of sodium lauryl sulphate, or other fatty alcohol sulphate.

also preferably containing .5 to 2 grams per. liter of sodium laurylsulphate or other fatty alcohol sulphate; then without rinsing, theplastic is sprayed with the n ckel Metal solution:

NiSO -6H O 3 lb., 5.5 oz. Citric acid -s 1 1b., 11 oz. Water to make 1gallon.

Reducer mixture:

NaOH 1 lb., 5.5 oz. Na,S O 11 lb., 11.5 oz. NaHz oz 1 1b., OZ-

The one gallon of metal solution is diluted to 20 gallons for spraying.The dry reducer mixture is also dissolved in water to give 20 gallons ofsolution.

As a specific example of nickel metal coating for electrolizing, wespray the above solutions separately at F. at 12 p.s.i. forapproximately 5 minutes on a Vinylite mold, backed by a cool metal plateto conduct away the heat.

We have obtained satisfactory results on copper, aluminum, stainlesssteel, steel, brass, and plastics. So far as we know, all types ofarticles can be nickel coated with our solutions.

Instead of using a spray process, the article can be coated by dippinginto a solution formed by mixing the nickel solution and reducersolutions, agitating the solutions, and then removing the coatedarticle. This procedure is not as fast and does not give a coating whichis quite as uniform as the spray process.

In order to facilitate ready comprehension of this invention and certainaspects of the method and means included within the purview of the same,a non-limiting example of apparatus or applying device useful forpractising some of the principles of the invention is illustrated in theaccompanying drawing.

While we have disclosed certain preferred embodiments of our invention,many modifications thereto may be made without departing from the spiritof the invention; and we do not wish to be limited to the detailedexamples, formulas, and proportions of ingredients set forth, but desireto avail ourselves of all changes within the scope of the appendedclaims.

We claim:

1. A process of coating a surface with nickel which comprises sprayingseparately and directing toward the surface so that the solutionsconverge on the surface a nickel solution and reducer solution, saidnickel solution consisting essentially of a nickel salt, selected fromthe group consisting of nickel sulphate, nickel chloride, and

, Patented o r. 18,1960,

140 F. for reducer sblui The plastic is then rinsed with to 10 grams of.silver nitrate per liter of aqueous SOlllilOIh.

hot spraying of plastics, the results are nickel formate; water, and"citric acid in a molar ratio of nickel sulphate to citric acid ofbetween approximately 1.3 and 2.0, and a molar ratio of such othernickel salts to citric acid. of between. approximately 1.3

and 2.85' and said reducer solution consisting essentially of analkaline solution of sodium hydrosulphite and sodium hypophosphite, themolar ratio of sodium hydrosulphite to sodium hypophosphite beingbetween approxi- V mately 1.40 and 3.53.

'2. The process of claim 1, wherein the metal solution 10 coating andthe temperature of the solutions is from 60 F. to 100 F.

References Cited in the file of this patent UNITED STATES PATENTS2,689,191 PC5881 Sept. 14, 1954 FOREIGN PATENTS 493,379 Great BritainOct. 25, 1938 OTHER REFERENCES Brenner et al.: Partof the Journal ofResearch of the National Bureau of Standards, Research Paper RP. 1835,vol. 39, November 1947, pp. 385-395.

15 Chakraborty et al.: J. Sci. Ind. Research (India) 138,

433-40 (1954), CA 49: 2808b.

Myers: Z. Anorg Chem. 80, pp. 93-103, CA 7: 21689.

1. A PROCESS OF COATING A SURFACE WITH NICKEL WHICH COMPRISES SPRAYING SEPARATELY AND DIRECTING TOWARD THE SURFACE SO THAT THE SOLUTIONS CONVERGE ON THE SURFACE A NICKEL SOLUTION AND REDUCER SOLUTION, SAID NICKEL SOLUTION CONSISTING ESSENTIALLY OF A NICKEL SALT, SELECTED FROM THE GROUP CONSISTING OF NICKEL SULPHATE, NICKEL CHLORIDE, AND NICKEL FORMATE, WATER, AND CITRIC ACID IN A MOLAR RATIO OF NICKEL SULPHATE TO CITRIC ACID OF BETWEEN APPROXIMATELY 1.3 AND 2.0, AND A MOLAR RATIO OF SUCH OTHER NICKEL SALTS TO CITRIC ACID OF BETWEEN APPROXIMATELY 1.3 AND 2.85 AND SAID REDUCER SOLUTION CONSISTING ESSENTIALLY OF AN ALKALINE SOLUTION OF SODIUM HYDROSULPHITE AND SODIUM HYPOPHOSPHITE, THE MOLAR RATIO OF SODIUM HYDROSULPHITE TO SODIUM HYPOPHOSPHITE BEING BETWEEN APPROXIMATELY 1.40 AND 3.53.
 4. THE PROCESS OF CLAIM 1, WHEREIN THE SURFACE IS AN ORGANIC PLASTIC SENSITIZED WITH STANNOUS CHLORIDE PRIOR TO COATING AND THE TEMPERATURE OF THE SOLUTIONS IS FROM 60* F. TO 100*F. 